Combining approaches for environmental assessment of rehabilitated gold-mining areas in the Eastern Amazon

Monitoring key soil and vegetation attributes in mining areas under environmental rehabilitation is essential to ensure that the intervention techniques are effective. There are several approaches to monitoring mining areas and their integration is necessary to process large amounts of information. Thus, this study aimed to (i) assess soil multi-contamination with potentially toxic elements (PTE) and human health risks; (ii) obtain a soil quality index with soil fertility data; (iii) calculate spectral index; (iv) show rehabilitation status based on vegetation attributes, and (v) compile these indices in a single measure. Four tailings' ponds (TPs), two waste piles (WPs), and an area of native forest from a gold mine in the Carajas National Forest were evaluated. Soil quality and vegetation cover are good in forest areas, with no evidence of PTE contamination. On the other hand, the TPs have poor fertility and vegetation cover, as well as higher levels of PTE. Human health risk indices obtained for all PTE were lower than 1, indicating a low risk to human health. The results of integrating the different indices suggest that the environmental conditions of the WPs are better than those of the TPs, which are still far from the environmental conditions of native areas. Soil attributes and vegetation development in TPs areas could be enhanced by the incorporation of organic materials and fertilizers and by planting species with phytoremediation potential. Finally, the integrative approach of the different indices proved to be useful in assessing the rehabilitation progress of the areas.